1. Field of the Invention
The present invention relates to a semiconductor device, and a method of manufacturing the device.
2. Description of the Related Art
A flash memory, which can hold memory even after power is turned off, is used in mobile devices such as a cell phone and also used in an FPGA (Field Programmable Gate Array) embedded with a logic circuit. Particularly, when the flash memory is embedded with the logic circuit as in the latter case, it is necessary to utilize each manufacturing process of the memory cell and the logic circuit well to prevent a problem from occurring in a logic-embedded memory to be shipped as a product.
In the logic-embedded memory, breakdown voltage of a tunnel insulating film that constituting the flash memory is monitored before shipping the product in some cases. However, because the tunnel insulating film is formed under a floating gate, in order to monitor the breakdown voltage by applying voltage from above and below the film, it is necessary that a conductive plug be directly contact the floating gate without contacting a control gate and test voltage be applied between the conductive plug and a semiconductor substrate.
For this reason, it is important how the process of the conductive plug contacting the floating gate is incorporated into the manufacturing process of a peripheral logic circuit.
The following Patent Documents 1 to 10 disclose various kinds of logic-embedded memory related to the present invention.
[Patent Document 1] Japanese Patent Laid-open No.6-97457 publication
[Patent Document 2] Japanese Patent Laid-open No.2003-158242 publication
[Patent Document 3] Japanese Patent Laid-open No.11-219595 publication
[Patent Document 4] Japanese Patent Laid-open No.2004-55763 publication
[Patent Document 5] Japanese Patent Laid-open No.10-56161 publication
[Patent Document 6] Japanese Patent Laid-open No.11-31799 publication
[Patent Document 7] Japanese Patent Laid-open No.10-189954 publication
[Patent Document 8] Japanese Patent Laid-open No.2003-37169 publication
[Patent Document 9] Japanese Patent Laid-open No.2003-100887 publication
[Patent Document 10] Japanese Patent Laid-open No.2003-124356 publication